Process for making thin pressed fibrous articles



March 20, 1934. G. J. MANSON 1,951,940

PROCESS FOR MAKING THIN PRESSED FIBROUS ARTICLES Original Filed Nov. 22,1928 2 Sheets- Sheet 1 7 I I V 21 22 25 1L a 4 J1 TI.E.\

I I mm Bangui/mum March 20, 1934. a. J. MANSON 1,951,940

PROCESS FOR MAKING THIN PRESSED FIBROUS ARTICLES 7 Original Filed Nov.22, 1928 2 Sheets-Sheet 2 Patented Mar. 20, 1934 PATENT OFFICE PROCESSFOR MAKING THIN PRESSED FIBROUS ARTICLES George James Manson,Hawkesbury, Ontario,

- Canada Application November 22, 1928, Serial No. 321,228 Renewed July1'7, 1933 12 Claims.

This invention relates to improvements in the process for making thinpressd fibrous articles such as dishes, trays, food containers and thelike, and the objects of the invention are to devise an improved processfor making an article of this type having one or more smooth faceswithout discoloration or hydration of the fibrous stock.

A further object is to devise an improved process for making such anarticle without drainage markings on the surface thereof.

A further object is to devise an improved process for rendering sucharticles waterproof and grease-proof.

Pressed fibrous articles have been formed for some time of ,wood pulpprincipally by expelling the moisture from the pulp stock betweensuitable dies, the result being that an impression of the die surfaceusually having wire thereon, through which the moisture may escape, isleft on the article.

Heat has in some instances been applied to facilitate the expulsion ofmoisture, but the heat has been applied under conditions, which causethe moisture to hydrate the surface fibres and discolour the article.

' The difficulty in avoiding hydration is greater when the article isthin, such as a dish or plate, as distinguished from a relatively thicksheet'of pulp stock.

I have discovered that a very much improved article may be produced, ifbefore the final surface treatment by smooth dies, a large amount of thewater content is removed, the final surface being finished by heattreatment with smooth dies.

The invention consists in the improved process as hereinafter moreparticularly described.

In the accompanying drawings is illustrated diagrammatically, a suitableapparatus for carrying out the improved process.

In the drawings:

Figure 1 shows a vertical section of a lower die used in the improvedprocess.

Figure 2 is a similar section of the lower die showing a closure capused therewith.

Figure Bis a vertical section of the lowe; die and an upper diecooperating therewith with a fibrous article in position between thedies.

Figure 4 is a vertical section showing a further step in the process inwhich the same lower die as shown in Figures 1, 2 and 3 cooperates witha heated upper die.

Figure 5 is a vertical section showing the final.

step in the process in which a heated lower die cooperates with anunheated upper die.

In the drawings like characters of reference indicate correspondingparts in the difierent figures.

The apparatus illustrated diagrammatically includes a lower die 10 whichmay be mounted in any suitable way for applying pressure thereto, suchas the hydraulic ram 11.

This die 10 is provided with a forming surface 12- which is providedwith drainage perforations 13 and below these perforations is a suctionchamher 14 which has a suction pipe 15 communicating therewith.

Surrounding the lower die 10 and slidably mounted thereon is acylindrical flange 16 which is normally urged upwardly in any suitableway, such as bysprings 17 so that in the position shown in Fig. 1 areservoir 18 for the reception of liquid stock is provided above thelower die.

A closure cap 19 (see Fig. 2) is adapted to cooperate with the lower die10 in one step of the process so as to close the reservoir 18 and apressure pipe 20 extends through this cap and connects with a reservoir18.

The usual wire mesh cloth 21 covers the forming face 12 of thelower die10.

In the step in the process illustrated in Fig. 3 thelower die 10cooperates with an upper die 22. In the step of the process illustratedin Fig. 4, the

, lower die 10 cooperates with an upper die 23 which upper die may beheated in any desired way and for purposes of illustration, in the formshown, the die 23 is provided with a heating chamber 24 to which maybefed in any desired way a heating medium such as steam or oil.

'In the final step of the process illustrated in Fig. 5, the upper die25 is unheated and a lower die 26 is heated in any desired way, such asexplained in connection with the upper die 23 in Fig. 4, and in the formshown this die 26 is provided with a heating chamber 27.

A fibrous article such as a dish being formed within the apparatus isindicated by the numeral 28.

In making a thin pressed fibrous article in accordance with the improvedprocess, the liquid stock which would contain about A to 2 fibre, isfirst fed into the reservoir 18 so as to cover the working face 12 ofthe lower die 10 as shown in Fig. 1 in which the level of the liquidstock is indicated by the broken line.

This liquid stock contains a suitable waterproofing substance which maybe in the form of a wax emulsion containing about 2 to 4% of wax.

Any suitable grease-proofing substance is also incorporated to theliquid stock.

The lower die 10 is then moved into engagement with the closure cap 19as illustrated in Fig. 2, and air pressure is led through the pipe 20,the pipe 15 being connected with the source of suction and in this stepa large amount of the moisture is expelled so that the moisture contentmay be reduced to about 70%. Also in this step the article 28 ispartially formed.

In the next step the lower die 10 carrying the article 28 is pressedagainst the upper die 22 (see Fig. 3) and the article is further formedand further moisture is expelled through the drainage perforations 13 inthe lower die which moisture is exhausted through the suction pipe 15.At the completion of this step the article is relatively dry, about 45%of the moisture having been expelled.

At the end of the operation shown in Fig. 2, the article is about 20% to25% pulp due to the air pressure on top. That is, the great bulk of thewater has been expelled which makes the pressing operation in Fig. 3much more simple. Instead of applying the cap 19 and air pressure I findthat I may, in this stage, simply apply a strong suction to pipe 15 withatmospheric pressure on top.

In the next step the lower die 10 carrying the article 28 is pressedwith substantial pressure against an upper die 23 (see Fig. 4) which dieis heated to a relatively high temperature in any desired manner andthis upper die 23 has a smooth heated face which produces, due to theheating and pressure, a smooth surface on the face of the article incontact with the upper die. In this step the steam or vapour generatedis drawn ofi through the suction pipe 15.

At the completion of this step I have produced a thin pressed fibrousarticle which has one smooth face, which face is entirely free fromdrainage markings.

If it is desired that the article have both faces thereof smooth andfree from drainage marks, it is subjected to a further step asillustrated in Fig. 5 in which the lower die 26, which has a smoothheated surface, is pressed against the article with substantial pressureso as to produce a smooth surface free from drainage markings on theface of the article in contact therewith so that at the completion ofthis final step shown in Fig. 5 I have produced a thin pressed fibrousarticle which has both faces thereof smooth and free from drainagemarkings.

In this last step since the faces of both the upper and lower dies 25and 26 are smooth, it

would probably be necessary to provide some means for the escape ofvapour and this could be done in any desired way, such for instance asimparting to the ram- 11 a vibratory motion so that the pressure betweenthe dies would be intermittent and thus provide what is known asbreathing of the die, so that this vapour might escape.

In my process a novel feature is that before the article is presented toa heated surface, a large amount of the water has been expelledtherefrom by simple pressing operations with the article in the coldstate and the article is not brought into contact with a heated surfaceuntil it is relatively dry. By thus having the article relatively drybefore it is presented to a heated surface, the tendency to hydrate thefibres which results in discoloration of the article is entirelyovercome, and it is found that the resulting article is not in any waydiscoloured.

Hitherto articles of this nature have been rendered waterproof andgrease-proof by coating the article after it is completely formed withwaterproofing and grease-proofing substances, but by my invention thewaterproofing and greaseproofing substances are incorporated into theliquid stock before the article is formed, so that this waterproofingand grease-proofing is not in the nature of a coating but permeates theentire article.

If the article is pressed during drying so that the natural tendency ofthe fibres to swell while the moisture is leaving them is resisted, amore rigid article, having a harder and smoother surface isproduced.This applies to an ordinary unsized and non-waterproofed andnon-greaseproofed article.

Now if the article has the waterproofing and grease-proofing materialsincorporated with the liquid stock thereof and is dried as above, thatis, if the article is pressed while it is hot, still moist and beingdried, that is as the sizing materials (including both the waterproofingand grease-proofing materials) are being set, not only is the articlegiven a harder and smoother surface as above but the sizing materials(including both the waterproofing and grease-proofing materials) aremuch more effective. The proposed treatment might be described as hotpressing the article while it is moist and the sizing materials(including both the Waterproofing and greaseproofing materials whichhave been incorporated in the liquid stock) are still unset. This is thetreatment given the article in accordance with the improved processherein described and it has been found to produce exceptionallysatisfactory results in the manufacture of thin wet-molded pressedfibrous articles such as dishes, trays, food containers.

I am aware that the. waterproofing and grease-proofing of paper has beenhitherto carried out by incorporating the waterproofing andgrease-proofing materials in the liquid stock, for instance as describedin my previous U. S. Patent No. 1,762,931 granted June 10th, 1930,application for which was filed on March 14th, 1927, but suchpreviousprocess relates to the manufacture of paper as made in the ordinarypaper making machines and does not relate to the manufacture of what maybe termed a wet-molded" article as in the present case and thefunctioning of the process and the results produced are very radicallydifferent. In this previous process there is no suggestion of hotpressing while the paper is moist and the size unset.

From the foregoing it will be apparent that I have devised an improvedprocess for making 1 thin pressed fibrous articles whereby the objectsof my invention have been attained.

It is to be understood that the drawings are purely diagrammatic andthat I do not wish to confine my invention to the particular form ofapparatus shown.

Various modifications may be made in my invention without departing fromthe spirit thereof or the scope of the claims and therefore the exactforms of apparatus shown and described 1 are'to be taken as illustrativeonly and not in a a limiting sense, and I desire that only suchlimitations be placed thereon as shall be imposed by the prior art orare specifically set forth in the claims.

What I claim as my invention is:

1. The method of forming a pressed fibrous article which comprises firstexpelling a large amount ofwater therefrom while cold by simple pressureand the passage of I air transversely through the article andsubsequently subjecting the article to a further drying action by heatand under mechanical pressure while simultaneously subjecting thearticle to suction.

2. The method of forming a pressed fibrous article which comprises firstexpelling at least 45% of the water therefrom while cold by simplepressure and the passage of air transversely through the article andsubsequently subjecting the article to a further drying action by heatand under mechanical pressure while simultaneously subjecting thearticle to suction.

3. The method of forming a thin pressed fibrous article which comprisesfirst expelling a large amount .of water therefrom while cold bypressing and subsequently subjecting the article to a further dryingaction by heat and under mechanical pressure while simultaneouslysubjecting the article to suction.

4. The method of making a waterproof fibrous article from liquid stockwhich comprises incorporating a water-proofing substance in the liquidstock, then initially forming the article by pressure and expelling alarge amount of water theretherefrom while cold, and then hot pressingthe article while it is still moist and the waterproofing material isstill unset.

5. The method of making a waterproof fibrous article from liquid stockwhich consists in adding- Wax in the form of an emulsion to the liquidstock, then initially forming the article by pressure an expelling alarge amount of water therefrom while cold, and then hot pressing theformed article while it is still moist and the wax unset.

6. The method of making a waterproof fibrous article from liquid stockwhich consists in adding an emulsion containing 2% to 4% wax to theliquid stock, then initially forming the article by pressure andexpelling a large amount of moisture therefrom while cold, and then hotpressing the formed article while it is still moist and the wax unset.

7. The method of making a grease proof fibrous article from liquid stockwhich consists in adding a grease-proofing substance to the liquidstock, then initially forming the article and the passage of airtransversely through the article, and subsequently subjecting thearticle to further drying action by heat and under mechanical pressurewhile simultaneously subjecting the article to suction.

' 9. The method of making a grease-proofing fibrous article from liquidstock, which comprises incorporating a grease-proofing substance in theliquid stock, then expelling a large amount of water therefrom whilecold by simple pressure and the passage of air transversely through thearticle, and subsequently subjecting the article to further dryingaction by heat and under mechanical pressure while simultaneouslysubjecting the article to suction.

10. The method of forming a fibrous article which comprises initiallyforming the article in aperforated forming die, subjecting the articleto mechanical pressure between unheated perforated forming dies andsimultaneously therewith causing a flow of air transversely through thedies and article under pressure therebetween, and then subjecting thearticle to a further drying operation by mechanical pressure in a heateddie while exhausting by suction the vapor generated.

11. The herein described method of forming a pressed fibrous articlewhich comprises initially forming the article from liquid stock bypressure in a forming die, then expelling a large amount of moisturefrom the initially formed wet and unheated article by mechanicalpressure thereof between unheated perforated dies and by simultaneouslywith said mechanical pressure exerting air pressure on one side of thedie and suction on the other side thereof whereby air under normaltemperature conditions and in the absence of any heating action on thearticle is forced transversely through the dies and article underpressure therebetween and prior to any heating of the article, andfinally subjecting the article to a further drying operation with heatand pressure in a smooth die. 1

12. The herein described method of forming a pressed fibrous articlewhich comprisesinitially forming the article from liquid stock bypressure in a forming die, then expelling a large amount of moisturefrom the initially formed wet and unheated article by mechanicalpressure thereof between unheated perforated dies and by simultaneouslywith said mechanical pressure exerting air pressure on one side of thedie and suction on the other side thereof whereby air under normaltemperature conditions and in the absence of any heating actionon thearticle is forced transversely through the dies and article underpressure therebetween and prior to any heating of the article, thensubjecting the article to a further drying operation with heat andpressure in a smooth die, and exhausting by suction the vapor generated.

GEORGE JAMES MANSON.

